Don't show the server unreachable banner while the client is suspended

homeserverReachabilityPublisher now reports unreachable while suspended so media loading parks instead of failing against a closed store. The reachability banner was keyed off the same publisher, so pausing the client would surface a spurious "Server unreachable" message.

Expose a separate homeserverConnectivityPublisher derived from the sync service state alone (it stays reachable while suspended) and key the banner off that, keeping the suspend-aware publisher for gating work that needs an open store.

ElementX/Sources/Mocks/Generated/GeneratedMocks.swift

@@ -2232,6 +2232,11 @@ nonisolated class ClientProxyMock: ClientProxyProtocol, @unchecked Sendable {
         set(value) { underlyingHomeserverReachabilityPublisher = value }
     }
     nonisolated(unsafe) var underlyingHomeserverReachabilityPublisher: CurrentValuePublisher<NetworkMonitorReachability, Never>!
+    var homeserverConnectivityPublisher: CurrentValuePublisher<NetworkMonitorReachability, Never> {
+        get { return underlyingHomeserverConnectivityPublisher }
+        set(value) { underlyingHomeserverConnectivityPublisher = value }
+    }
+    nonisolated(unsafe) var underlyingHomeserverConnectivityPublisher: CurrentValuePublisher<NetworkMonitorReachability, Never>!
     var userID: String {
         get { return underlyingUserID }
         set(value) { underlyingUserID = value }